The Total Solar Irradiance Calibration Transfer Experiment (TCTE) is studying solar energy to help scientists understand the causes of climate change on our planet. Incident sunlight—the sunlight that falls directly on a surface—is the primary energy source that drives Earth’s climate. TCTE measures total solar irradiance (TSI), or the total light coming from the Sun at all wavelengths, in order to monitor changes in the incident sunlight at the top of Earth’s atmosphere. The mission mitigates a potential and likely upcoming gap in an otherwise continuous 34-year climate data record following the loss of the NASA Glory mission in 2011.
Successfully launched on November 19, 2013, TCTE is a payload onboard the U.S. Air Force Space Test Program spacecraft known as STPSat-3, which was developed and built by Ball Aerospace.
- The Total Solar Irradiance Monitor (TIM)
- TIM Principal Investigator, Greg Kopp
The TIM instrument measures TSI, the spatially and spectrally integrated solar radiation incident—the Sun’s net energy output—at the top of the Earth’s atmosphere. TIM continues a solar climate data record that has been compiled by NASA and NOAA since 1978 and is used to determine the sensitivity of the Earth’s climate to the natural effects of solar forcing. LASP has refined TIM for improved accuracy since its first launch on the Solar Radiation and Climate Experiment (SORCE).
TIM monitors the incident sunlight to the Earth’s atmosphere using an ambient temperature active cavity radiometer. Using electrical substitution radiometers (ESRs) and taking advantage of new materials and modern electronics, the TIM measures TSI to an estimated absolute accuracy of 350 ppm, or 0.035%. Relative changes in solar irradiance are measured to less than 10 ppm/yr (0.001%/yr), allowing determination of possible long-term variations in the Sun’s output.
For more information about the Total Irradiance Calibration Transfer Experiment (TCTE), see: http://lasp.colorado.edu/home/tcte
Launch date: November 19, 2013
Launch location: Wallops Island, Virginia
Launch vehicle: Minotaur I
Mission target: Low-Earth orbit
Mission duration: 18 months
Other organizations involved:
- Ball Aerospace
- U.S. Air Force